One of the areas of increasing and serious public concern is the disposal of environmental solid waste. Contributing to this disposal concern is the growing amount of expendable packaging materials, and plastic packaging materials in particular. A large part of solid waste consists of plastic packaging, of which about one-third are cushioning materials used to support and protect relatively fragile contained articles. One of the most common of these is expanded polystyrene.
There are numerous articles which are either nonself-supporting or which require adequate cushioning support of protruding contours, edges and surfaces to prevent damage and breakage from sideways movement or from external compression and hence loss. This need is particularly great to prevent breakage and loss from shifting of electronic instruments, glass, porcelains and other like relatively delicate articles in transit or movement. Consequently, many manufacturers are looking for environmentally friendly, yet inexpensive, replacements which are alternatives to plastic in the area of inner packaging, in particular.
There is also an ongoing need for a lightweight, yet strong material suitable for filling the void space around a contained article and to protectively cushion the article from damage during storage or shipment. Some of this need has been fulfilled to some extent by plastic cushioning materials, such as moldable polyethylene copolymer, expanded foams of polyethylene or polystyrene, styrene acrylonitrile, and polyurethane, polyethylene air bubble packaging, polystyrene "popcorn" and "peanuts", and cellulose-based cushioning materials like curled wood shavings, popcorn, crumpled, shredded or corrugated paper and kraft honeycomb structures.
However, many of the cushioning materials are either not recyclable, or even if recyclable, tend to be expensive and lack the combined lightness, strength and rigidity provided by a paper honeycomb structure. Because of its great supportive strength and durability in combination with its lightness, low cost and recyclability, a paper honeycomb structure has long been desirably employed for material handling and protective packaging.
Paper honeycomb structures are typically made of kraft and can distribute weight evenly to support static loads to about 12,000 pounds and dynamic loads to about 3,000 pounds. Specifically, a paper honeycomb structure provides a lower cost, thicker protective reinforcing material with higher strength than that provided by corrugated structures made of comparable kraft. The term "corrugated" is intended to refer to the well-known reinforcing material consisting of a series of parallel elongated crests, commonly called flutes, to which inner and outer paper liners are typically secured. More importantly, a paper honeycomb structure is also a recyclable article and, thus, is a desirable environmentally friendly, inexpensive, lightweight and strong alternative to plastic.
In particular, void fillers and interior packaging for protecting relatively delicate products, typically having a fragility requiring moderate protection against about 40 to about 85 peak deceleration (G's) should desirably cushion against damage or breakage from multiple impact. However, while biodegradable materials, including conventional paper honeycomb structures, generally offer adequate supportive protection against a single impact, they show limited protection against multiple impacts. For example, as a cushioning material, a conventional paper honeycomb structure ordinarily affords generally adequate protection against single impacts at moderate levels of protection, but its shock absorbing characteristics for multiple impacts require more weight and more volume than do polymeric cushioning materials.
Thus there is still a need, therefore, for an economical protective resilient inner packaging material that can cushion against multiple impacts, yet is preferably as strong, lightweight, inexpensive and recyclable as a paper honeycomb structure. The resilient prestressed honeycomb structure prepared by the method and apparatus of the present invention meets these needs.